These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Broken Aesop - The movie makes no distinction between either murder and killing in self defense, or carrying weapons for protection and carrying weapons for criminal purposes. In essence, the movie boils down their message to to all killing and all guns are bad.
Michael Sullivan, Jr.: I saw then that my father's only fear was that his son would follow the same road. And that was the last time I ever held a gun.
Averted in the graphic novel, which eschews any kind of moral meaning in favor of a "just the facts, ma'am" approach to the story.
Tear Jerker - Who doesn't feel sorry for a little boy who's just lost his mom and little brother and is on the run from hitmen aiming to kill him and his father?
John Rooney's role in the end serves as this. He knows already that his son has been embezzling from him for years and it's hinted that Michael was closer family to him than Connor ever could be. However, despite realizing that Connor's death is imminent, he refuses to give him up, instead imploring for Michael to leave with his own son while he can. When Michael eventually returns to kill Rooney (as well as his entire entourage), the old man can only solemnly remark that he's glad that Michael would be the one to kill him.